So what tells them when it’s time to make that switch?

A Stress Signal That Changes Cell Behavior

The same Rockefeller research team has now identified the key signal behind this transformation. Hair follicle stem cells respond to what’s called an integrated stress response (ISR) — a cellular alert system that helps them conserve energy and focus on survival tasks.

In the skin, this stress response is tied to the amino acid serine, a non-essential nutrient found in common foods like meat, grains, and milk. In their study published in Cell Metabolism, the scientists showed that when serine levels fall, the ISR activates and hair production slows down. If the skin is also wounded, the ISR ramps up even further, stopping hair growth entirely so that cells can concentrate on repairing damaged tissue. This shift in priorities helps the skin heal faster.

“Serine deprivation triggers a highly sensitive cellular ‘dial’ that fine tunes the cell’s fate — towards skin and away from hair,” explains first author Jesse Novak, an MD-PhD student at Weill Cornell’s Tri-Institutional MD-PhD Program and former doctoral student in the Rockefeller lab of Elaine Fuchs. “Our findings suggest that we might be able to speed up the healing of skin wounds by manipulating serine levels through diet or medications.”

Adult tissues depend on stem cells to maintain balance — replacing cells that die and repairing tissue when it’s damaged. Yet, scientists still know little about how these cells manage their energy and nutrients during different tasks. Novak and his team wanted to understand the metabolic factors that keep stem cells functioning normally and what changes when they must shift gears to heal a wound.

“Most skin wounds that we get are from abrasions, which destroy the upper part of the skin,” says Novak. “That area is home to a pool of stem cells that normally takes charge in wound repair. But when these cells are destroyed, it forces hair follicle stem cells to take the lead in repair,” Novak says. “Knowing that, we thought that tracking these skin cells through wound healing presented a very good model for testing if and how metabolites are regulating this process overall.”

Serine’s Role Beyond Hair and Skin

Earlier research from the Fuchs lab showed that precancerous skin stem cells can become dependent on circulating serine and that limiting serine in the diet helps stop these cells from turning cancerous. Those findings highlighted serine’s powerful influence on cell behavior and even inspired studies testing serine-free diets as cancer treatments.

However, it remained unclear how reducing serine might affect healthy tissue. To explore this, Novak focused on serine’s role in normal stem cell activity and how its absence might reshape regeneration.

The researchers tested how hair follicle stem cells respond to metabolic stress. They either deprived mice of dietary serine or used genetic methods to block the cells from producing their own. In both cases, the results showed that serine communicates directly with the ISR — a system that monitors when tissue conditions go off balance.

When serine levels were low, hair growth slowed because it requires significant energy. When wounds occurred, the ISR activated even more strongly, prioritizing healing over hair regeneration. In other words, when stress increases, the skin’s repair mechanisms take priority.

“No one likes to lose hair, but when it comes down to survival in stressful times, repairing the epidermis takes precedence,” says Fuchs. “A missing patch of hair isn’t a threat to an animal, but an unhealed wound is.”

Can Extra Serine Boost Hair Growth?

Once the team confirmed that low serine levels affect stem cell behavior, they wondered about the reverse — could increasing serine levels enhance hair growth? The answer appears to be no. The body maintains tight control over serine levels, and even when mice were given six times more dietary serine than usual, levels only increased by about 50%.

“However, we did see that if we prevented a stem cell from making its own serine and replenished its losses through a high-serine diet, we were able to partially rescue hair regeneration,” Novak adds.

Next, the researchers plan to investigate whether wound healing can be improved by lowering serine intake or by using medications that influence serine levels or the ISR pathway. They also aim to test other amino acids to see if any have similar effects.

“Overall, the ability of stem cells to make cell fate decisions based upon the levels of stress they experience is likely to have broad implications for how tissues optimize their regenerative capacities in times where resources are scarce,” says Fuchs.

The number of people living with diabetes is expected to climb to 750 million by 2045. While modern drugs can control symptoms, many come with side effects and do not address the underlying causes of metabolic imbalance. This has led scientists to revisit nature’s medicine cabinet in search of new therapeutic options. Among these is Nitraria roborowskii Kom, a tough shrub that thrives in the harsh deserts of western China. Its bright red fruits, sometimes known as “desert cherries,” have nourished and healed local communities for centuries. Only recently have researchers begun to uncover the biological mechanisms behind its traditional use, prompting systematic scientific investigations into its potential.

Breakthrough Study Confirms Potent Diabetes-Fighting Properties

A collaborative study between Qinghai University and the Northwest Institute of Plateau Biology, published in the Chinese Journal of Modern Applied Pharmacy, provided strong experimental evidence of the fruit’s effects. Using well-controlled trials, scientists tested a concentrated form of the extract (NRK-C) on diabetic mice over seven weeks. The results were striking: the compound not only lowered blood sugar and improved insulin responsiveness but also addressed broader metabolic dysfunctions through a previously underexplored biological route.

How the Desert Berry Restores Metabolic Balance

The detailed analysis revealed the extract’s impressive range of benefits. Over the course of seven weeks, NRK-C reduced fasting blood glucose levels by 30-40% in diabetic mice, with stronger results at higher doses. It also improved insulin sensitivity by roughly 50% compared with untreated animals. In addition to these improvements, the extract balanced cholesterol and lowered oxidative stress markers by as much as 60%, a rare feat for any single therapeutic compound.

Further investigation showed that NRK-C works by reactivating the PI3K/AKT signaling pathway — a critical metabolic circuit that often breaks down in diabetes. This reactivation appears to “reboot” the body’s ability to regulate glucose and fat metabolism. Microscopic examination supported these findings, revealing healthier liver and pancreatic tissue structures in treated mice compared with untreated ones. Taken together, these findings suggest the compound helps the body reset its metabolic function rather than just masking symptoms. Its naturally broad effects contrast sharply with the narrowly targeted mechanisms of many pharmaceutical drugs.

Expert Insight: A Holistic Approach to Diabetes Treatment

“These results are exciting because they suggest we might be able to treat diabetes more holistically,” said Dr. Yue Huilan, a senior researcher on the project. “Instead of just lowering blood sugar like most medications, this plant extract appears to help the body regain its natural metabolic balance. The implications could extend beyond diabetes to other conditions involving insulin resistance.” While the team emphasized that human trials are still needed, the findings represent an encouraging move toward more natural and comprehensive approaches to diabetes care.

This discovery opens up several promising research directions. Pharmaceutical developers may pursue standardized NRK-C extracts as supplements or adjunct therapies, while nutrition experts could explore adding the fruit to functional foods aimed at metabolic health. The results also lend modern scientific support to traditional medicinal knowledge, helping bridge ancient practice and contemporary medicine. Researchers are particularly eager to determine whether NRK-C could help prevent diabetes in high-risk individuals or reduce complications in those already affected.

More broadly, the findings underscore the value of preserving and studying traditional medicinal plants, many of which may hold untapped potential for addressing modern health challenges. Nature, it seems, still has many healing secrets waiting to be rediscovered.

The findings, published November 6 in Monthly Notices of the Royal Astronomical Society, question the long-accepted belief that a mysterious force known as “dark energy” is pushing galaxies apart at an ever-increasing rate. Instead, researchers found no convincing evidence that the universe is still accelerating.

If confirmed, the results could reshape scientists’ understanding of dark energy, help resolve the long-standing “Hubble tension,” and transform theories about the universe’s past and future.

Evidence for a Cosmic Slowdown

Lead researcher Professor Young-Wook Lee of Yonsei University in South Korea said, “Our study shows that the universe has already entered a phase of decelerated expansion at the present epoch and that dark energy evolves with time much more rapidly than previously thought.

“If these results are confirmed, it would mark a major paradigm shift in cosmology since the discovery of dark energy 27 years ago.”

For nearly three decades, astronomers have believed that the universe’s expansion was accelerating due to dark energy, a mysterious force acting as a kind of “anti-gravity.” This conclusion was originally based on measurements of distant type Ia supernovae, a discovery that earned the 2011 Nobel Prize in Physics.

Rethinking the Universe’s “Standard Candles”

The new research from Yonsei University challenges that foundation. Type Ia supernovae, long considered reliable “standard candles” for measuring cosmic distances, appear to be influenced by the age of the stars that create them.

Even after standardizing their brightness, the team found that supernovae originating from younger stars tend to look fainter, while those from older stars appear brighter. Analyzing data from 300 host galaxies, the researchers confirmed this age effect with an extraordinary level of confidence (99.999%).

This means that part of the dimming once attributed to cosmic acceleration could actually result from stellar population differences rather than universal expansion.

A New Model Emerges

When the team corrected for this age-related bias, the supernova data no longer fit the standard ΛCDM model, which assumes a constant form of dark energy. Instead, it matched more closely with a newer model supported by the Dark Energy Spectroscopic Instrument (DESI) project.

This alternative model draws on baryonic acoustic oscillations (BAO) — essentially ancient sound waves from the Big Bang — and data from the cosmic microwave background (CMB). Both sources suggest that dark energy is not constant but instead weakens and changes over time.

When researchers combined the corrected supernova data with BAO and CMB results, the evidence became overwhelming: the universe does not appear to be accelerating anymore, but has entered a phase of decelerated expansion.

A Universe Already Slowing

Professor Lee explained, “In the DESI project, the key results were obtained by combining uncorrected supernova data with baryonic acoustic oscillations measurements, leading to the conclusion that while the universe will decelerate in the future, it is still accelerating at present.

“By contrast, our analysis — which applies the age-bias correction — shows that the universe has already entered a decelerating phase today. Remarkably, this agrees with what is independently predicted from BAO-only or BAO+CMB analyses, though this fact has received little attention so far.”

Testing the Findings

To strengthen their conclusions, the Yonsei team is performing what they call an “evolution-free test.” This approach examines only supernovae from young, coeval galaxies — those with stars of similar ages — across the entire redshift range. Early results already support the main finding.

“Within the next five years, with the Vera C. Rubin Observatory discovering more than 20,000 new supernova host galaxies, precise age measurements will allow for a far more robust and definitive test of supernova cosmology,” said research professor Chul Chung, a co-lead author of the study, along with PhD candidate Junhyuk Son.

The Vera C. Rubin Observatory and the Future of Cosmology

Located high in the Chilean Andes, the Vera C. Rubin Observatory houses the world’s most powerful digital camera. Having begun scientific operations this year, it is expected to revolutionize our understanding of both the solar system and the broader universe.

After the Big Bang, roughly 13.8 billion years ago, the universe expanded rapidly before gravity slowed it down. Then, around nine billion years after its birth, scientists discovered that expansion had begun speeding up again. This was attributed to dark energy, which is believed to make up about 70 percent of the universe.

Dark Energy’s Mystery Deepens

Despite decades of study, dark energy remains one of science’s most puzzling enigmas. Last year, data from DESI in Tucson, Arizona hinted that the influence of dark energy might have changed over time, an idea now gaining traction with the Yonsei team’s new results.

With advanced instruments like DESI and the Vera C. Rubin Observatory, astronomers hope to finally uncover what dark energy really is — and how it shapes the fate of the universe.